In a compact turbocharger such as an automobile turbocharger, an axial-flow turbine which rotates a turbine wheel with fluid flowing in the axial direction has been recently developed to replace the conventional radial turbines for the purpose of restricting turbo lags with reduced inertia, for example.
FIG. 10 is a schematic cross-sectional view of a configuration of an axial-flow turbine for a turbocharger.
As illustrated in FIG. 10, an axial-flow turbine 100 for a turbocharger includes a housing 120, and a rotational shaft 104 and a turbine wheel 110 accommodated in the housing 120.
The rotational shaft 104 is rotatably supported on the bearing 102 about the center axis CL. A hub part 106 of a cylindrical shape is disposed on an axial end of the rotational shaft 104. Further, a shaft sealing part 102a for sealing the circumferential face of the rotational shaft 104 is disposed between the bearing 102 and the hub part 106. A plurality of rotor blades 108 protrude outwardly in the radial direction from the flat circumferential face 106a of the hub part 106. The hub part 106 and the plurality of rotor blades 108 constitute the above described turbine wheel 110.
The housing 120 accommodates the above turbine wheel 110. A rotational shaft housing section 126 is formed inside the housing 120, for accommodating the rotational shaft 104 in the vicinity of the center axis CL and about the center axis CL. A scroll part 122 and a bend section 124 are formed around the rotational shaft housing section 126. The scroll part 122 swirls the exhaust gas introduced into the housing 120 around the rotational shaft 104. The bend section 124 directs the flow of the exhaust gas having flowed out from an outlet 122a of the scroll part 122 in the axial direction. Further, a downstream flow path section 128 is formed on the downstream side of the turbine wheel 110. The exhaust gas, having flowed from the scroll part 122 through the bend section 124 to rotate the turbine wheel 110, flows into the downstream flow path section 128 and then exits into an exhaust gas channel (not illustrated) from the downstream flow path section 128.